Long-distance practical quantum key distribution by entanglement swapping

Understand

We develop a model for practical, entanglement-based long-distance quantum key distribution employing entanglement swapping as a key building block.

• Relying only on existing off-the-shelf technology, we show how to optimize resources so as to maximize secret key distribution rates.
• The tools comprise lossy transmission links, such as telecom optical fibers or free space, parametric down-conversion sources of entangled photon pairs, and threshold detectors that are inefficient and have dark counts.
• Our analysis provides the optimal trade-off between detector efficiency and dark counts, which are usually competing, as well as the optimal source brightness that maximizes the secret key rate for specified distances (i.e.